Determination Dawn of Shadiq in Masalembu Island by Using Image Processing Sobel Edge Detection Technique
The value of the sun's elevation -20 below the horizon as criteria for Subuh prayer began to be reviewed again by researchers and fuqaha. The results of some research were different with Ministry Religion Affairs and raise doubts for some Muslims then need to require re-verification. Astrophotography and image processing techniques are introduced to solve this problem. The rising of morning twilight can be detecting and analyze by image processing because the image before and after will have different pixel values. Capturing image as the data of this research started when the altitude of the sun is -23˚below the horizon. The duration of capturing the picture every once in a minute. After the image has been collected in 7 days, Sobel image processing utilizes to identify the edge of the horizon when the dawn light appears. Combining proper setting camera calibration with nice weather, the Sobel operator's edge detection successfully detects dawn shadiq as the beginning of subuh prayer. The value of the sun's altitude obtained in this research based on image processing is -19.7128 with a standard deviation (σ) of 1.114429.